1. Field of the Invention
The invention relates to a dispenser unit having a flexible polymer bag, a joining part, and an inflexible hard part, wherein the joining part has an inner layer, welded to the hard part, and an outer polymer layer, welded to the inner material of the flexible bag, processes for manufacturing it, and its use.
2. Background Information
Such dispenser units are used for storing and dispensing liquids and in particular are physiologically safe heat-sterilizable bags which are manufactured from transparent polymers, such as polyolefin materials, and have at least one hard part, which is sterilizably joined to the bag material via a joining piece; that is, the welded connection between the bag and the hard part easily withstands (steam) sterilization temperatures of at least 121.degree. C. The bag should be transparent so that any changes in the liquids contained in it, such as sedimentation, clouding, etc., are immediately apparent. Such bags are used for instance in medicine as blood bags, bags for dialysis liquids, plasma, etc., but are also optionally suitable for other aqueous solutions, such as beverages, and so forth.
Thousands of similar flexible containers are in use and in the prior art are primarily made from soft PVC. PVC is favorable because it can be readily bonded tightly to polycarbonate, which is the usual material for hard parts, and also forms a transparent, flexible film. However, PVC has meanwhile become undesirable for various reasons. PVC, if it is to be able to offer the physical properties of flexibility that are demanded, must contain plasticizers. These plasticizers, such as diisooctylphthalate, have a tendency to migrate out of the PVC and into the liquid contained in the bag. Thus, over the time such PVC bags are used, a long-term dialysis-dependent patient might absorb several grams of plasticizer, which is extremely objectionable physiologically and can cause permanent damage to the patient. Aside from this, PVC is problematic to dispose of, because of the occurrence of chlorine compounds when it is combusted, and attempts have therefore already been made to replace it with nonhalogenated compounds. Thus far, however, it has been highly problematic to achieve the favorable properties of PVC, namely the very good, problem-free weldability and transparency with high liquid tightness and good water vapor barrier properties, with other materials at commercially feasible expense.
For instance, it is known from German Patent Disclosure DE 32 47 294 A1 for bags of a polyolefin, such as polyethylene, to be welded to a hard part, made for instance of polycarbonate, by means of a tubular joining piece that is a polyethylene copolymerized with vinyl acetate, and subsequently to cross-link this composite by radiation, thus making the connection between the PE of the bag and the PE of the joining part sterilization-proof. In the non-cross-linked state, the polyethylene copolymerized with vinyl acetate begins to flow at sterilization temperatures; it is thus necessary for the entire arrangement that has this material to be cross-linked.
Because the weld seam between the joining part and the polycarbonate part is made first and only after that is the vinyl acetate and polyethylene copolymer cross-linked so that the bond withstands the high sterilization temperatures, the bag is sterilization-proof. However, the radiation cross-linking entails considerable effort and expense, because all of the complete dispenser units have to be brought to a suitable radiation source and treated there.
Also in this prior art, the selection of material for the bag is greatly limited, since a polyolefin that can be welded to the polyolefin-containing EVA always has to be used as the inner material of the bag, because otherwise the connection to the PC part and to the inside of the bag is not assured.
A similar arrangement is known from German Patent Disclosure DE-A 33 05 365. It describes PVC-free sterilizable bags that have an outer layer of polyamide, usually PA 66, adhesive, and a mean-density polyethylene as the inner layer.
These bags are physiologically unobjectionable, since the polyethylene contains no plasticizers and is at least equal in quality PVC bags--except that they are very complicated to manufacture and that the MD polyethylene (medium-density polyethylene) used is expensive.
From European Patent Disclosure EP 380 270, a tubular material for attachment to the patient or for introducing additional material into a flexible bag, which can optionally be welded to a polycarbonate hard part, has been disclosed in the form of a three-layer tubular material which can be sealed on the outside to polycarbonate by means of ultrasound, microwaves, or heat.
This sterilizable tube has an outer layer with polypropylene, ethylene propylene copolymer, or an ethylene propylene copolymer modified with a thermoplastic elastomer, which can be sealed to polycarbonate, while an intermediate layer that makes the joining piece flexible may be a very low-density propylene, ethyl vinyl acetate copolymer, modified or unmodified ethylene methylacrylate copolymer, polyvinylidine chloride, ethyl vinyl acetate and modified ethylene methylacrylate copolymer, a mixture of ethyl vinyl acetate and very low-density propylene, or a modified ethyl vinyl acetate; the inner layer should have the most heat-resistant polymer material possible, such as a copolyester, polypropylene, ethylene propylene copolymer, polyurethane, PVC, or a mixture of a copolyester with ethyl vinyl acetate.
Preferably, a material for the hose is used that has already been cross-linked via chemical cross-linking agents during coextrusion, to improve the temperature resistance (sterilizability) of the welded bond, or that can be radiation cross-linked afterward, since otherwise the material will not maintain its properties under sterilization conditions and will flow away. This known joining part is designed to be joined on the outside to polycarbonate and has a complicated structure--which is the connection with the flexible bag. This is not accordingly a joining part but rather a tube for liquids that is to be connected to the polycarbonate part and that naturally must be autoclavable.
In European Patent Disclosure EP-A 56 42 31, a coextruded joining part for the problem of joining a flexible bag to a polycarbonate hard part is proposed which as its outer layer has a polyolefin polymer material that has a melt flow index of approximately 12.
The inner layer here is bonded to an intermediate layer, which lends flexibility to the joining part and may for instance be SBS, and is embodied as a joining layer containing ethyl vinyl acetate, which is to be secured to the polycarbonate. This arrangement again requires the usual provision of cross-linking the bag after the joining part is welded thereto, for instance by means of radiation, to make the arrangement sterilizable.
From German Patent Disclosure DE 44 27 175 (Coster), it has become known for a flexible bag with a multilayer foil that has as its outer layer a polyamide or polyester layer to improve mechanical strength, with an inner layer of polyethylene or polypropylene, to be welded to a connection tubule that has an outer layer of polyethylene, polypropylene or the like, since polyethylene and polypropylene can be readily welded well only to themselves or to one another. As the hard part, to which the inner layer of the joining part is welded, polyacetal is proposed. However, this arrangement has the disadvantage of not being heat-sterilizable.
International Patent Disclosure WO 93/23108 (Baxter) addresses the problem of a joining part for flexible bags with PVC, which is extruded here in three layers and has as its outer layer a polypropylene copolymer/styrene ethylene-butylene-styrene copolymer mixture and an inner layer of PVC. The use of PVC, however, is usually undesired, for the reasons given above.